BLA: Martinez and Kesner (1991)

Martinez and Kesner, 1991

On Acetylcholine and its Role on Memory Formation

Before reading, you should be comfortable with:
- neurotransmitters
- the principles of the biological level of analysis
- experimental methods used in the biological level of analysis

What is this study about?
This study was performed in the biological perspective, where lab rats were used to test the role that a neurotransmitter has in the formation of memory.

Aim?
To see the role that acetylcholine has on memory formation.

How was this "formation of memory" tested with lab rats?
The lab rats were put under three different controls:
1. Rats were injected with scopolamine (drug), which is known to block acetylcholine receptor proteins on the post-synaptic neurones. This means that acetylcholine, a hormone expected to help form memories cannot travel from one neuron to another, i.e. no nerve impulse is sent across neurones.
2. Rats were injected with physostigmine, a drug that is antagonistic towards acetylcholinesterase. Cholinesterase (or acetylcholinesterase) is what cleans up the acetylcholine from receptor proteins on the post-synaptic neurones, returning the neurones to their "resting potential", where no nerve impulse is being sent. Physostigmine blocks cholinesterase which prevents this "cleaning-up" of acetylcholine.
3. Rats were not injected or altered in any form at all.

Design: 
- Laboratory experiment
- Controlled variables (i.e. 3 conditions of the rats, drug amount, maze complexity)

Procedure:
1. All rats were placed in the maze individually and completed the maze (maze had reward of food at the end)
2. Rats were given their respective treatments (see 3 groups above)
3. Rats were placed in maze individually and time taken to complete maze was measured

Results?
- Condition 1 (rats that were injected with scopolamine) took the longest to complete the maze
- Condition 2 (rats that were injected with physostigmine) took the shorted amount of time to complete the maze
- Condition 3 (rats with no treatment) had maze-completion times between the condition 1 and condition 2 rats 

Interpretation?
- Scopolamine has the effect of preventing or slowing down the process of memory formation. This can be concluded because the rats given scopolamine took the longest to complete their mazes. Acetylcholine is involved in memory formation because scopolamine is what blocks acetylcholine receptors.
- Acetylcholine is involved in memory formation because the condition 2 rats were quickest in completing the maze: their injection of physostigmine prevented the removal of acetylcholine from the receptor proteins of the post-synaptic neurones.
- The more acetylcholine is available, the more productive memory formation is. This can be concluded because condition 3 rats were in-between the other two conditions in terms of maze-completion time.

Advantages of this experiment?
- The experimental method of this experiment makes it clear to see the cause-effect chain between the neurotransmitter acetylcholine and memory formation.
- Conclusions drawn from this experiment are therefore accurate.
- Multiple trials could have been easily performed
- Easily replicable
- Possiblity that humans can be treated with acetylcholine or physostigmine for memory-loss
- No differences in the role of acetylcholine between cultures (as rats were used, not people); results may be relevant for every human
- No people were harmed in this experiment
- No deception was used in this experiment

Disadvantages of this experiment?
- Rats were harmed
- Ethical concerns to the extent that the rats suffered
- The results cannot be completely applied to humans
 

BLA: All About Neurotransmitters

Neurotrasmitters

• The Biological Level of Analysis in IB psychology suggests that there are physiological origins of many behaviors
• The Biological Level of Analysis suggests that human beings should be studied as biological organisms
• This view is controversial, so IB psychology attempts to approach human behavior with a holistic view -- considering the cognitive, biological and socio-cultural factors that a person experiences daily -- to determine origins for human behavior
• The relationship between cognition and biology are bidirectional -- cognition can affect biology, while biology can affect cognition
• Many physiological factors play a role in human behavior, such as:
• Brain processes
• Neurotransmitters
• Hormones
• Genes

Let us first review the three principles of the BLA before proceeding...

1. Behavior can be innate

2. Studying animal behaviors can help us understand human behavior

3. There are biological components to behavior -- such as a neurotransmitter for a certain trait

The BLA is often criticized for trying to break down complex and complicated human behavior down into its smallest component parts -- such as into a specific molecule, hormone, neurotransmitter. This is too simplistic an approach to take when we are trying to analyze complex organisms. "There are no easy answers to complex questions"

-N E U R O T R A N S M I T T E R S-

A. Neurons (nerve cells) are one of the building blocks of behavior. Neurons can make up to 13 trillion connections with each other.

B. Neurons relay electrochemical messages to the brain, so the organism can respond to internal and external stimuli

i) When electrochemical messages are sent to the brain, this is called neurotransmission

ii) When an electrochemical impulse travels down the body of the neuron, neurotransmitters are released and cross the synapses (gaps) between the neurons. 

iii) Neurotrasmitters can be considered as the body's natural chemical messengers which transmits information transmits information from one neuron to another neuron

C. Neurotransmitters have a range of different effects on human behavior, such as:

1) Mood 

2) Memory

3) Sexual arousal

4) Mental illness

- E X A M P L E -

Martinez and Kesner 1991 - The Role of the Neurotrasmitter Acetylcholine on Memory Formation -

•  Aim: To see the role that acetylcholine (a neurotransmitter) has in memory formation 
• Acetylcholine: believed to play a role in memory formation, thus the experiment was testing this assumption / hypothesis
• Procedure: The rats learned how to complete a maze that had food at the destination. The rats were then separated into three different groups and:

• Group 1: A group of rats injected with scopolamine, which blocks acetylcholine receptors on the neurons, thus decreasing the available acetylcholine.
• Group 2: A group of rats injected with physostigmine, which blocks the clean up process of cholinesterase, which is responsible for the clean up of acetylcholine from the receptors.
• Group 3: A group of control rats, not treated with anything
• Results: The rats in Group 2 were able to complete the maze quicker than any other rats of the other groups. Group 1 was slowest at completing the race. The control group (Group 3) was able to complete the race at an average pace.
• Interpretation: Acetylcholine is responsible for the formation of memory, as the rats that had blocked acetylcholine receptors were unable to complete the race as efficiently as the other rats. On the other hand, we can also confirm that acetylcholine is responsible for the formation of memory because Group 2 (that had been injected with physostigmine, a compound that prevents cholinesterase from cleaning up the receptor sites and ridding the sites of acetylcholine) was quickest at finding its way through the mazes.

Evaluation of this experiment: